1. Field of the Invention
The present invention relates to a guide wire, for example, used for introducing various kinds of catheters.
2. Prior Art
In the case of inserting a catheter into an organism, a front end portion of the catheter is introduced by inserting the guide wire into a lumen of the catheter and operating this, so that a selection of branching a blood vessel can be smoothly and securely performed.
As a conventional guide wire, there has been known a guide wire which is constituted by a stainless steel or a superelastic alloy (Ni--Ti alloy).
In this case, since an insertion of the catheter within the organism is performed under an X-ray irradiation, an X-ray contrast characteristic is applied to the catheter.
Recently, in a medical field, an examination and a diagnosis are performed in accordance with a magnetic resonance imaging method (MRI). Due to a progress of the technology, it is also possible to insert the catheter and a guide wire into a body of a person to be examined while monitoring an image by MRI, thereby performing a medical activity such as an examination and a diagnosis.
In this case, the conventional guide wire constituted by a stainless steel is magnetized due to a material characteristic thereof and a work hardening generated during a wiring process. Therefore, the guide wire is placed in a strong magnetic field of the MRI, a large artifact (an image not existing) appears on an MRI monitor image due to an excess reaction, and the guide wire is recognized as ten times greater in diameter than an actual thickness. As a result, a position of the front end portion of the guide wire within the organism can not be accurately recognized, which might cause incorrect medical activities as mentioned above.
Further, the guide wire heated by a strong magnetizing effect of the MRI, may also cause incorrect medical activities as mentioned above or giving a bad influence to the organism.
On the contrary, in the conventional guide wire constituted by the superelastic alloy (Ni--Ti alloy), the artifact generated on the MRI monitor image appears in a smaller diameter than the actual size of the guide wire, so that it is hard to recognize a position of the front end portion of the guide wire in the organism.